This invention relates to strain relief cable boots and dust covers designed to shield against electromagnetic interference (EMI) generated by high-speed data communication modules, computers and peripheral devices.
Transmission cables may be used to transmit data between workstations, mainframes and other computers, as well as provide data connections to mass storage devices and other peripheral devices. Data may be transferred using a variety of transmission cable technologies, including multimode optical fiber cables, single mode optical fiber cables, and copper cables (e.g., twinax and coax copper cables). Standard pluggable transceiver modules have been developed to transition between different transfer media and the electronic components inside a computer or peripheral device. A pluggable transceiver module produces a standardized output in accordance with prescribed protocols, regardless of the medium (e.g., optical fiber or copper) through which the data is transmitted or received. A transceiver module typically plugs into a transceiver receptacle that extends out of the rear panel of a computer or peripheral device. The transceiver receptacle connects the transceiver module to a motherboard or circuit card in the computer or peripheral device.
Strain relief systems generally protect transmission cables against the stresses that might result during handling of the cables. In particular, strain relief systems protect against stresses that otherwise might impair the signal transmission properties of the cables. Fiber optic cables are especially vulnerable to damage caused by overstressing or kinking, especially near the cable connectors. A typical strain relief system includes an elongated boot that extends proximally from the proximal end of the cable connector. The boot surrounds the cable and confines it to a prescribed bend radius range, thereby protecting the cable from excessive bending in the region of the cable-connector interface. The boot may guide the cable proximally from the connector in either a straight or a curved path.
Many computers and other high-speed electronic equipment produce significant amount of electromagnetic radiation. As a result, such equipment typically is housed inside enclosures that are designed to contain the electromagnetic interference (EMI) emissions from the electronic equipment. Significant EMI levels, however, may be released through transceiver receptacle openings in the electromagnetically shielded enclosures. EMI also is generated by the transceiver modules that plug into the receptacle openings. Various complex techniques for reducing the total EMI levels generated at the respective interfaces between the electromagnetically shielded enclosure, the pluggable transceiver module and the transmission cable have been proposed.
The invention features an EMI-shielding strain relief boot and an EMI-shielding dust cover.
In one aspect of the invention, an EMI-shielding strain relief boot includes a flexible elongated boot body and an EMI shield. The boot body has a proximal end, a distal end, and an inner surface defining a bore sized and arranged to contain an end portion of a transmission cable and an associated cable connector. The EMI shield extends along a substantial length of the boot body and is configured to shield a region of the bore from interfering electromagnetic radiation. The distal end of the boot body is slidable over the cable connector and is conformable to and envelopable about at least a portion of a pluggable transceiver connector.
In another aspect, the invention features an EMI-shielding strain relief boot having a flexible elongated boot body and an inner surface defining a bore with a uniform radial dimension. The thickness between the inner surface and an exposed outer surface of the boot body tapers from a central longitudinal region toward the proximal end of the boot body and toward the distal end of the boot body. The boot also includes a flexible electromagnetic interference (EMI) shield that extends along a substantial length of the boot body to an exposed surface of the distal end of the boot body. The EMI shield is formed from an electrically conductive material and is configured to shield a region of the bore from interfering electromagnetic radiation.
Embodiments may include one or more of the following features.
The boot body preferably is configured to limit the bend radius of the transmission cable near the cable connector. The boot may include a proximal flange coupled to the proximal end of the boot body and defining an opening sized to engage the cable connector while accommodating the end portion of the transmission cable. The boot body may include an exposed outer surface with one or more gripping features. A distal flange may protrude outwardly away from the bore. The distal end of the boot body may have an inner surface that flares outwardly away from the bore. The bore may define a curved path through which the transmission cable may extend.
The EMI shield preferably extends to an exposed surface of the distal end of the boot body. The EMI shield preferably comprises an electrical conductor (e.g., a plurality of electrically conductive particles, or a plurality of electrically conductive wires). The EMI shield may be incorporated into the boot body. The EMI shield may include an electrically conductive layer disposed on the inner surface of the boot body. The EMI shield may include magnetic material. The boot body preferably comprises an elastomer.
In another aspect, the invention features a data transmission system, comprising: a pluggable transceiver and an associated transceiver connector; a transmission cable and an associated cable connector sized and arranged to engage the pluggable transceiver connector; and one of the above-defined strain relief boots. The distal end of the boot body is slidable over the cable connector and is conformable to and envelopable about an interface between the transmission cable connector and about the pluggable transceiver connector.
The pluggable transceiver preferably is insertable into a transceiver receptacle having a proximal end defining an opening for receiving the pluggable transceiver. The distal end of the boot body is slidable over the cable connector and is conformable to and envelopable about the proximal end of the transceiver receptacle.
In another aspect, the invention features a method of electromagnetically shielding an opening in an electronic apparatus enclosure. In accordance with this inventive method, an electromagnetic interference shielding strain relief cable boot is attached over a flange protruding from the opening in the electronic apparatus enclosure.
In another aspect of the invention, the dust cover has a flexible elongated dust cover body and an EMI shield. The dust cover body has a proximal end, a distal end, and an inner surface defining a bore sized and arranged to contain a flange protruding from an opening in an electronic apparatus enclosure. The EMI shield extends along a substantial length of the dust cover body and is configured to shield a region of the bore from interfering electromagnetic radiation. The distal end of the dust cover body is conformable to and envelopable about the flange protruding from the opening in the electronic apparatus enclosure.
Among the advantages of the invention are the following.
The inventive strain relief boots protect transmission cables from damage that might be caused by overstressing or kinking. At the same time, these strain relief boots enable a user to quickly and easily extend the electromagnetic shielding properties of an electromagnetically shielded electronic equipment enclosure to the respective interfaces between the transmission cable, a pluggable transceiver module and a transceiver receptacle extending through the enclosure. The inventive EMI-shielding strain relief boot and dust cover provide relatively inexpensive ways to effectively protect against interfering electromagnetic radiation generated near the pluggable transceiver openings in electronic apparatus enclosures.
Other features and advantages of the invention will become apparent from the following description, including the drawings and the claims.